Ventilation Improvements for Veal Calf Housing

Current Situation

Multiroom veal buildings usually have a service or preheat alley from which air can be drawn into the calf room. Currently, many calf room air inlets consist of manually adjusted panels in the feed aisle door. As fans cycle on and off or variable speed fans ramp up and down in speed, the fixed opening does not accommodate the changing air flow needs, and proper air distribution is not maintained. The self-adjusting inlet baffle is ideal for providing adequate air volume and mixing for mechanically ventilated veal calf rooms. These inlets are described in Self-Adjusting Baffle Inlet to Improve Air Distribution. One large baffle inlet assembly (Figure 1) over each feed aisle entry door is advisable to supplement the feed aisle door inlet. A second and third assembly to each side can provide hot weather ventilation when some air flow over the calves is desirable for cooling.

Overview if Solution

Using a 50-calf room of two rows of stalls facing a central feed aisle as an example, an inlet design would look like Figure 2. Cold weather, minimum ventilation is provided by the door panel, which directs air along the feed aisle and virtually eliminates any cold air draft on the tethered calves. As weather warms, additional fans turn on and the self-adjusting baffle inlet above the feed aisle door opens to provide additional inlet area. This single baffle inlet should be sized to provide inlet area, in concert with the door panel, for cold and mild weather conditions. Air will be directed along the ceiling where it can mix with warm room air before reaching the calves. Once hot summer weather arrives, the two additional self-adjusting baffle inlets located over the calf stalls are unlocked to provide inlet area needed for large summer air exchanges. These two larger baffle inlets have their baffles locked into a closed position most of the year and are only opened during hot weather.

Ventilation Sizing Review

cold: 10 cfm/100-pound (cwt) calf
mild: 20 cfm/cwt
hot: 50 cfm/cwt

Provide 1.7 to 2.0 square foot of inlet area per 1000 cfm of fan capacity to maintain a 0.05- inch static pressure difference between outdoors and the calf room interior.

This works out to:
cold 2.75 sq. in inlet/cwt
mild 5 sq. in inlet/cwt
hot 13 sq. in. inlet/cwt

Table A provides inlet area and fan capacity needed per calf to meet these requirements for calves growing from 100 up to 500 pounds during cold, mild, or hot weather conditions. Figure 6 shows the inlet size needed per calf depending on ambient temperature (weather) and calf weight.

Ventilation Example Calculations

50 veal calves; 2-row, central feed aisle room off preheat aisle as shown in Figure 3.

Cold weather; smallest calves at 100 pounds each.
Fan capacity: 50 calves x 10 cfm/cwt = 500 cfm
Inlet size: 50 calves x 2.75 sq. in./100 pounds = 138 sq. in. ≈ 1 sq.ft.

Cold weather; large calves at 450 pounds each.
Fan capacity: 50 calves x 10 cfm/cwt x 4.5 cwt = 2250 cfm
Inlet size: 50 calves x 2.75 sq. in./cwt x 4.5 cwt = 619 sq. in. = 4.3 sq. ft.

Table B provides inlet area and fan capacity needed for an example 50-calf room housing calves from 100 to 500 pounds during cold, mild, or hot weather conditions. Figure 7 shows the inlet area and fan capacity needed in the 50-calf room for various weight calves during each season.

Year-round Ventilation Inlets

Cold Weather

The minimum winter ventilation needs for moisture removal in the calf room is estimated at 10 cfm/100- pounds (cwt) of calf and can be met using an adjustable panel in the feed aisle entry door. A permanent opening of 1 sq. ft. matches the inlet area needed for minimum cold weather ventilation rate for 50 of the smallest calves (100 pounds each). In the example, an 8-inch tall by 18-inch wide inlet is provided (Figure 2). As calf size increases to 500 pounds, the door panel is opened wider to match calf growth increments of 50 pounds. This matches the increased fan air exchange rate needed for larger calves. The winter ventilation rate controls moisture and air contaminant (ammonia, odor, etc.) removal. It provides a minimum air exchange to achieve these functions while recognizing that supplemental heat is being used to warm room air.

One inherent disadvantage of a single inlet at one end of the room is that calves near the door panel are exposed to fresh air while calves unfortunate enough to be located closer to the fans are continually breathing stale air. As long as room length (feed aisle length) is kept below 75 feet, this should not be a problem. The 50-calf room meets this criteria with 25 calves per row in 24- to 26-inch wide stalls (larger stalls would be used for the heavier calf market weight of 400 to 500 pounds) for a 50- to 55-foot-long room.

Mild Weather

As weather warms, more fan capacity is needed, estimated at 20 cfm/cwt, for temperature control in the room, and hence, more inlet area is needed. Additional inlet area, beyond that minimum area provided by the open door panel, will be supplied by the self-adjusting baffle inlet box above the door (Figure 4). The baffle inlet box should be no more than 12-inches high to encourage air to discharge near the ceiling for more effective fresh air "throw" into the room. Place the baffle inlet box flush against the ceiling. A box 12- inches high and 70-inches wide, a typical feed aisle width, will provide enough inlet area for mild weather ventilation rates for all but the largest (500-pound) calves on the warmest spring or fall days. An option is to be able to draw air from the preheat aisle for youngest calves and from the attic for older calves which do not need the preheated air (Figure 5 and Drawing Set C).

Hot Weather

As weather changes to hot summer conditions, even more fans are used for temperature control, at 50 cfm/cwt, so even more inlet area is needed. This is provided by the two self-adjusting baffle inlets located to the sides of the feed aisle. They are larger than the central inlets and provide benefit in directing some air flow over the calves for convective, breezy cooling on hot days. Evaporative cooling fogger nozzles may be added near these inlets for enhanced cooling. These larger inlets are fixed shut most of the year and only used during summer. They need to be 18-inches high by 75-inches long to provide adequate inlet area for the maximum air flow rates needed in the 50-calf room example. During hot weather, the feed aisle door panel is fixed in its full open position, the central aisle 12-inch by 70-inch baffle is operating, plus the two large summer baffles. When cool weather returns in the fall, the two large summer inlet baffles should be fixed shut, and only the central aisle baffle inlet and the door panel opening are used.

Fans

Provide fans that supply the required range of air capacity needed for moisture and excess heat removal. Controls are necessary to maintain desired room temperature in concert with supplemental heaters. Using Table B for the 50-calf room example:

Stage 1

Minimum continuous ventilation, cold weather
Variable speed, 16-inch fan
Do not operate below 50% speed.
700 to 2500 cfm provided as calves grow 100 to 500 pounds.

Stage 2

Mild weather ventilation
Variable speed, 18-inch fan
900 to 3800 cfm as temperature increases
(3400 to 6300 cfm total stages 1 + 2)

Stage 3

Hot weather ventilation
Variable speed 24-inch fan; probably operated as on/off
Additional 5600 cfm
(11,900 cfm total stages 1 + 2 + 3)

Stage 4: Heat

1000 Btu/calf estimate. Depends on insulation in building and ventilation rate.
Provide 1000 Btu/calf heat in each calf room: 50,000 BTU heater.
Provide one similar-sized heater in the preheat alley.

Controls

Use four-or five-stage computer controller with two variable speed outputs (stages 1 and 2) and two thermal contacts (stage 3 and 4-Heat). Fifth stage may be used for evaporative cooling in hot weather. Manual override switches on each stage are recommended. Thermostat backup on minimum ventilation fan is needed. Controller with temperature curves will accommodate the growing calf ventilation needs. Controller that brings stage 1 variable speed fan up to full speed before activitating stage 2 variable speed fan is desirable. Provide max-min thermometer at calf level in room to monitor temperatures on a daily basis.

Summary

Adjustable inlets help provide proper fresh air distribution in veal calf housing. Manually adjusted inlets are not repositioned often enough to provide appropriate conditions when fans are changing speeds and/or cycling on and off. The self-adjusting inlet baffle assembly is a relatively easy retrofit for existing housing. Units may be purchased from manufacturers or made on site. Either way, the sizing and location guidelines provided here will improve calf room air distribution.

Inlet area/Calf (sq. inches/calf)
Cold = 10 cfm/100 lbs. and 2.75 sq. inches/100lbs.
Mild = 20 cfm/100 lbs. and 5 sq. inches/100lbs.
Hot = 50 cfm/100 lbs. and 13 sq. inches/100lbs.
Ventilation rate/Calf (cfm/calf)